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Basic requirements for dimensioning Dimensioning of basic body, cutting and interpenetration bodies
Dimensioning general composite solids
Exercises Dimensioning Composite Solids
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Reasonableness:The dimensions must be marked according to the requirements of design, manufacture and test.Basic requirements for dimensioning Correctness: There should be no mistake with all dimensions and the national standard (GB) should be observed. Correctnessintegrityclarity reasonableness. Integrity : The dimension must fully define the size of the part and the relative locations of individual components. It can not be skipped, nor repeated. Clarity : The arrangement of the dimensions should be clear and clean.1. Basic requirements for dimensioning
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Each dimension of the part should mark on the drawing only once. It should also be marked on a drawing that most clearly represents the corresponding constructs. The true size of the spare part is based on the dimension marked on the drawing and has nothing to do with the size of the drawing and the accuracy of the drawings. 2) There is no need to mark the unit of dimensions if it is mm. One only needs to mark the dimensions if the units are not mm, such as cm or 30.Basic requirements for dimensioning2. Basic rules of dimensioningAll dimensions marked on the drawing are dimensions of the final part. Otherwise one needs to clearly indicate on the drawing.
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383.Dimension construction18 Dimension line is usually drawn perpendicular to the extension lines and the extension lines should extend beyond the terminal of dimension line for about 23mm. Extension line
142899An extension line is drawn with a continuous thin line. An extension line originates from a feature outline, an axis line, or a center line.
9Basic requirements for dimensioningDimension line and its terminals
It must be drawn using continuous thin line and can not be in coincident with any existing lines or drawn as extension of any lines.
The dimension line must be parallel with line segment being dimensioned. The distance between the dimension line and the nearest feature should be about 810mm. All distances between neighboring dimension lines should be as consistent as possible and are usually between 68mm. Arrowhead is equal to 1b thick and 4b length. b=the continuous thick line Dimension text
18 3822 Dimension text should be marked above or left the dimension line. All linear dimensions should be marked heading upwards for horizontal dimensions, heading towards the left for vertical dimensions.
Dimension text can also be entered in the breaking space of the dimension line. When there is 30 for horizontal line, dimension text can also be placed somewhere else using a leader line.2222 Orientation of linear dimensions
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One usually needs to mark all dimensions of length, width and height. For body of revolution, it only needs to mark its radial dimension (the diameter symbol is added before the dimension figure) and axial dimension.
1. Dimensioning the basic partDimensioning of basic body,cutting and interpenetration bodies
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Dimensioning of basic body,cutting and interpenetration bodies2. Dimensioning of subtraction/cutting type solid When dimensioning cutting type composite solid, there are also dimensions for defining location of individual shape elements, such as cutting planes, in addition to the above shape dimensions. As the intersection curve is uniquely defined with basic shape dimensions and location dimensions, there is no need to dimension intersection curves. intersection curveintersection curvelocation of cutting planeslocation of cutting planeslocation of cutting planesintersection curvelocation of cutting planes
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Dimensioning of basic body,cutting and interpenetration bodies3. Dimensioning of union/interpenetration type part There are also location dimensions in addition to shape dimensions for union/interpenetration type parts. With shape and location dimensions, the interpenetration curves are uniquely defined, and there is no need either to dimension interpenetration lines.interpenetration linelocation dimensionslocation dimensions
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Dimensioning of basic body,cutting and interpenetration bodies4. Dimensioning of supporting board elements All center-to-center spacing of holes, screw threads and grooves on the board should be dimensioned. Since the basic shape of the board and the distribution of holes and grooves are different, the formats of location dimensions for dimensioning center-to-center spacing are also different.
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Dimensioning general composite solids 1.Selection of dimension datum There should be at least one dimension datum for each of the three principal directions for length, width and height of the composite solid. Length datumXHeight datumZWidth datumY1 Dimension datum Dimension datum indicates common starting position of related dimensions.
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1Datum face error2 Commonly datum of dimensioning Dimensioning general composite solids Height datum Symmetry plane or the bottom surface. Length datum Symmetry plane or the end surface. Width datum Symmetry plane or back-end surface.
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Coordinates origin intersection curveintersection curveCenter line 3) Datum mark Center point Dimensioning general composite solids Center axes 2) Datum line
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Chain dimensioning a b c Combined dimensioning a b c 3 Form of commonly dimensioningParallel dimensioning a b c Dimensioning general composite solids Avoidance of dimensions into a series with an overall dimensionsCombined dimensioning is suitable
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Dimensioning general composite solids 2.Correctness and integrity in dimensioning(2) Location dimensions show the relative location relationships between individual shape elements. (3) Overall dimensions show the overall length, width and height of the composite solid.Shape dimensions show sizes, such as length, width and height, of the basic part and its building elements. Center of holes must be given clearly
Over-dimensionedOverall length added as an auxiliary Overall length must be given clearly
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Dimensioning general composite solids 3.Clarity and reasonableness in dimensioning(1) Dimensions should be marked in the view that most reflects the characteristics of the related shape and location. RextendMarked in bevelMarked in bulgeDashedlineoverall dimensionsRadius symbol RDiameter symbol
R
R
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Marked it symmetricallyDimensions should be marked in the view that most reflects the characteristics of the related shape and location. Dimensions should not be marked on dashed lines as far as possible.SymmetrySymmetryMarked in the same view as possible2 Dimensioning general composite solids
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Larger dimensions placed outside smaller dimensions(3) All dimensions should be better arranged outside individual view in order to avoid possible overlap of dimension lines and feature lines of the drawing. They should also be arranged following the principle of Larger dimensions placed outside smaller dimensions. (4) For diameters of cylinders and cones, the dimension should be better marked in a non-circle view as far as possible. Dimensioning general composite solids
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There should be no dimension for intersection lines.intersection curveintersection curveinterpenetration lineintersection curve Dimensioning general composite solids
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2. Dimension this drawing of components. 3. Point out the dimension which one is incorrect and correct it. Exercises1. Point out the dimension which one is incorrectly.
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1. Point out the dimension which one is incorrectly.
Avoidance of dimensions into a series with an overall dimensions
(1)
(2)
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2. Dimension this drawing of components.P24
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3. Point out the dimension which one is incorrect and correct it. RROmit.